1. Technical Field of the Invention
The invention relates to a prosthetic implant for supplementing existing body tissue contours. Thus the implant might be used to augment the contours of a person's breasts, pectorals, chin, calves, and the like. In particular, the invention relates to a prosthesis made up of multiple layers of lubricated material which simulate the tactility and motility of natural body tissues when the implant has been placed within a person's body.
2. Prior Background Art
Tissue simulating, body implants are probably most readily associated in people's minds with mammary prosthesis. Because of this ready association, the invention will be disclosed in terms of a mammary implant to be used for purposes of breast reconstruction or augmentation. However, it is emphasized that this is done for purposes of exposition only. No attempt at limiting the use of the invention is intended. The teachings disclosed herein are applicable to tissue simulating implants of various types including those implanted within a person's chin, pectoral muscles, calves, and the like.
Most tissue simulating prosthesis provide a container, often referred to as a sac or a lumen in the prior art. The lumens are generally inflated with a liquid or gel to add volume to the prosthesis when positioned within a person's body. Tiffany in U.S. Pat. No. 4,731,081 discloses that the single lumen prosthesis is the most realistic. However, fluid filled lumens all display a problem in that they appear to be susceptible to damage and subsequent leakage of the fill material into the body tissues of the person in which the implant is made. The recent notoriety of persons allegedly suffering bodily harm as a result of a leakage of silicone gel from implanted prosthesis exemplifies the concern with which effective prosthesis design must be approached.
Tiffany notes that the lumen often develops a crease causing opposite walls of the lumen to bear on and frictionally remove material from each other. If the removal of material becomes sufficient, the wall is ruptured and the inflating fluid leaks into the body tissues. To inhibit such frictional wear, Tiffany adds a lubricant to the inflating fluid used to inflate the lumen. The lubricant is chosen so as not to separate or settle out from the inflating liquid. Tiffany teaches that the lubricant shall be less than 70 percent of the total of the liquid-plus-lubricant within the lumen, only 5 to 10 per cent by weight.
In U.S. Pat. No. 3,934,274, Hartley, Jr. teaches of a two lumen prosthesis. The inner lumen in anchored to the walls of the outer lumen. As the inventor Becker, referred to hereinafter, will later note, the placement of one lumen within another, wherein each lumen has an anchor point which places a limitation on the mobility of one lumen to move within the other, creates a center for high concentration of shearing forces. As one lumen moves within the other, flexing about its anchor point, leaks frequently occur.
Tiffany places 100-300 cc of silicone gel within his inner lumen, 75-125 cc of saline solution in his outer lumen. He teaches that the outer lumen may be semi-permeable to permit an exchange of fluid between the sac and body tissue. Leakage of silicone gel into the body tissues as well as the insertion of the prosthesis within the body-tissues often causes capsular contracture of the tissue about the implant. The implant in turn contracts so as to assume a spherical shape. This spherical contracture usually results in an unrealistic tissue outline which is rigid and tense. Hartley teaches that some of the saline solution may be removed from the outer sac so as to decompress the sac to defeat the spherical contracture of the prosthesis.
Chaglassian, in U.S. Pat. No. 4,650,487, builds upon the Hartley prosthesis in that he provides three lumens, as opposed to Hartley's two. All lumens are anchored together and thus suffer the sheer force, potential for damage noted above. The outermost lumen in Chaglassian's prosthesis is deflatable so as to relieve the effects of spherical contracture. The innermost lumen is a high profile container intended to provide high projection of the breast.
Another inventor seeking to provide high projection of the prosthesis augmented breast is Cronin. In U.S. Pat. No. 4,790,848, Cronin teaches a two lumen prosthesis. However, unlike the earlier prosthetic devices noted above, Cronin teaches that the inner lumen shall be free floating; it must be small relative to the outermost lumen having only 25 to 60 per cent of that volume of that outer lumen; and, it must be spherical in shape. Cronin emphasizes the spherical shape of the inner lumen. He is critical of earlier implants in which the inner lumen has the same general shape and approximate size as the outer lumen. The reasons given for Cronin's criticism are that an inner lumen having the same general shape and approximate size of the outer lumen is limited in motion and maintains no projection of the breast.
A two lumen, free floating structure is taught by Becker is U.S. Pat. No. 4,944,749. Through a unique valving arrangement, disclosed by Becker, both inner and outer lumens may be inflated after insertion within the body of the patient. Becker inflates his outer lumen with 40-50 cc of a viscous gel. Following Tiffany's lead, Becker notes that the gel has desirable lubricating characteristics.
However, he treats the lubrication aspects as an incidental benefit since the gel, 40-50 cc in volume, functions primarily as an inflating fluid for the outer lumen.
In its varying aspects, the prior art discloses an awareness of implant prosthesis which make use of multiple lumens. However, the prior art requires that each of the lumens making up a given prosthesis shall be inflated with a significant volume of fluid since each of the prior art prostheses depends primarily on the inflating fluid to produce desirable tactility and motion. None of the prior art disclosed relies on a multiplicity of lubricated walls wherein the plurality of walls and the lubricity of relative motion among the plurality of walls imparts the desired tactility and movement of natural body tissue when a prosthesis, so structured, is implanted in a patient's body.